In medium bowl, combine sour cream and milk until well blended. In 9-inch by 9-inch ceramic or glass baking dish, arrange 3 tortillas in single layer, tearing 1 tortilla in half to fit. Top with one-third each of the salsa and the sour cream mixture, all of the black beans, one-third of the cheese, and one-third of the sliced poblano peppers, in that order, spreading each in an even layer. Repeat layering two more times, with refried beans in center layer and pink beans on top. (Can be prepared to this point up to 1 day ahead; cover and refrigerate.) Place baking dish on jelly-roll pan to catch any drips, and bake uncovered 40 to 55 minutes or until mixture bubbles and top browns.